Thursday

November 27, 2014

November 27, 2014

Posted by **pyhsiclover** on Wednesday, May 22, 2013 at 2:11am.

Is your answer 0.57?

A 15 kg, 1m wide door which has frictionless hinges is closed but unlocked. A 400 g ball hits the exact middle of the door at a velocity of 35 m/s and bounces off elastically, thereby causing the door to slowly swing open. How long in seconds does it take for the door to fully open (rotate 90 degrees)?

- pyhsic question for count iblis -
**Count Iblis**, Wednesday, May 22, 2013 at 12:25pmThe answer I posted was correct as far as I can see, the problem may well be a typo in the problem itself, e.g. a 400 gram ball slamming into the door at the speed of a speeding car is not going to "slowly" open the door.

Anyway, it's a complete waste of time to e.g. try to see if what was meant is 3.5 m/s. I would suggest forgetting about this problem and moving on to another problem, you simply say that you did the problem correctly, that the teacher made a mistake and that you demand full marks for this problem.

- pyhsic question for count iblis -
**j**, Wednesday, May 22, 2013 at 8:33pmiblis got the problem right. for those trying to use jiskha to cheat on the brilliant problems, there was a mistake made in the acceptable answers for this week's question.

- pyhsic question for count iblis -
**roger**, Friday, May 24, 2013 at 10:02amibis ,I beg to differ,the door slowly open because the ball bounces back elastically,please don't be certain,when u are wrong

**Answer this Question**

**Related Questions**

Inter. Algebra - Another problem plz help Count Iblis. How do you solve 5/x+2 + ...

Chemistry: Answer check please! - 1. Reactions follow the law of conservation of...

MATH - how many milligrams are there in a kilogram I give up alejandra. I showed...

Ms. Sue, quick question... - do you know if "Count Iblis" is a real "Count", as ...

Algebra! - Six pears and three apples cost $3.90. Two pears and five apples cost...

Different Question Count Iblis...Please help! - If 3x - 7 = -4, then x = 1. ...

Calculus - Integrals - I made this question, just wanted to make sure it didn't ...

math - input:1 output:49 input:2 output:48 input:3 output:47 what is the rule? p...

Math: Homework Questons (answer quick) - Can you check if the answer is correct...

Physics - A trap door, of length and width 1.65 m, is held open at an angle of ...